Gypsum board sheets are fastened to sheet metal building studs by self drilling and tapping screws. Commercially, the screws are inserted by electrically powered screw guns which rotate at about 2500 rpm. The screw point moves rapidly through the soft gypsum board and the outer layers of paper on both faces of the sheet, but when the point of the screw reaches the outer surface of the metal stud, it is essential that the screw penetrate the metal stud in the shortest possible time and without hesitation. If the screw hesitates, i.e., the screw gun continues to rotate the screw rapidly without forward motion of the screw or with a greatly diminished velocity, the screw threads will strip the threads made in the gypsum board and in effect, the screw will become a drill auger and bring to the surface of the gypsum board, the soft gypsum. Further, the screw threads will rip and tear the paper surface of the gypsum board and the ragged edges of the paper will protrude from beneath the edges of the head of the screw. The paper edges, known as "frizzies" in the trade, must be hand picked from the gypsum board wall so that the thin coat of plaster can properly cover the screw heads to leave a smooth unblemished wall surface.
Numerous approaches to the "point" problem have been taken. Some screw manufacturers have patented special chisel points such as Knohl, U.S. Pat. No. 3,207,023.
Some manufacturer's have attempted to form a sharp point by using an eight threads per inch design so that there will be sufficient material at the point end of the screw to form the necessary sharp unthreaded cone portion at the tip.
The problem with the eight thread per inch screw for fastening to sheet metal, however, is the fact that thread pitch or spacing between the threads exceeds the thickness of the metal and the thread lacks holding power with the metal.